Epitaxial silicon is used in a variety of semiconductor devices when a pure silicon layer is required. Selective epitaxial growth of silicon in a vertical transistor is one such device. Epitaxial silicon is grown on a substrate and exhibits the same crystal structure as the substrate on which it is grown. Dislocations and stacking faults, which form during epitaxial silicon growth, are primary concerns as they are electrically active due to the presence of dangling bonds and lead to numerous problems. Such problems include, but are not limited to, unnecessary recombination generation currents, lower breakdown voltages, high leakage and larger junction ideality factors.
In contrast with dislocations, which primarily lie on the surface of epitaxial silicon, stacking faults extend into the surface and can originate at the bottom and/or sidewalls of a container structure during epitaxial silicon growth. Stacking faults that originate at the bottom and propagate all the way to the surface of a column of epitaxial silicon will lead to leakage of charge from the capacitor and also provide an alternate path for electrons to travel through the transistor. These defects need to be effectively controlled for a vertical transistor to function.
Thus, there remains a need for selectively growing epitaxial silicon which controls the direction of propagation of bottom stacking faults. In addition, there remains a need to reduce the number of stacking faults that propagate all the way through to the surface of a column of selectively grown epitaxial silicon.